Since the dawn of anatomically modern humans around 200,000 years ago, we have striven to develop every substance that would allow us to evade natural selection and to have complete control over our present and our future. Despite this, we have continued to follow certain evolutionary behaviours - ones that improve the chances of our genes being passed on. Isn’t this a surprise? I have often been fascinated by this paradoxical behaviour.

Particularly one trait that I keep noticing in couples, recently: they are nearly always of a similar attractiveness level, at least, as perceived by today’s society. In an age when environmental factors probably play a bigger role than genetic ones - when beauty is no longer the sole indication of social standing, and power and money can be acquired with one click of a button - we are still judging our mates by the laws of our ancestors: “pick someone with whom you are most likely to produce genetically successful offspring”. This seems odd to me.

Further to my own everyday observations, there is in fact a body of work that witnesses the existence of this phenomenon. Dr. Elaine Hatfield, professor of psychology, at the University of Hawaii, and her colleagues explained this phenomenon with her ‘matching hypothesis’ in 1966. The hypothesis claims that people form and succeed at committed relationships with someone who are “equally socially desirable” - similar level of physical attraction, intelligence, or social standing.

Theoretically, individuals are influenced by both the desirability of the potential match and their perception that their affections will be reciprocated. Dr. Hatfield’s team referred to such mating choices as “realistic choices”, because they are influenced by the chances of having one’s affection reciprocated. One of the research studies carried out by her team supports this theory [1]. The research team chose 752 students randomly and their physical attractiveness was rated by four independent judges, giving each person an ‘attraction rating’. When these individuals were paired with someone of the opposite gender and then sent to a dance, couples with similar attraction ratings were far more likely to continue interacting with one another following that evening. This was a seminal piece of work by Dr Hatfield, developing a new area in social psychology and laying the foundations for a number of follow-up studies.

The results of matching hypothesis research studies may seem rather intuitive, but the existence of such behaviour today seems unlikely, considering the presence of manufactured success in present society. Furthermore, experiments have shown this matching behaviour is also present between same-sex couples, a phenomenon that cannot be explained by the notion of having offspring with “good genes”. So, why does this still happen?

It seems that subconsciously we still associate physical attractiveness with other positive attributes, such as intelligence, wealth and improved breeding success and it leads individuals to rate aesthetic appeal as an important factor in the initial stages of a relationship. This is known as the ‘halo effect’ [2]. However, the halo effect does not explain why, on average, human beings, who are generally a very aspirational species, choose to settle with their equal rather than striving for someone more attractive.

Huston, in 1973 [3], suggested that the answer to this behaviour lies more in social psychology than biological evolution. Here it was argued that the matching hypothesis did not stem from matching at all, but rather from the tendency of people to avoid rejection; they pick a mate who is similarly attractive to avoid being rejected and discarded for someone more attractive than them.

Hatfield has since conducted further research into this field [4], tying the matching hypothesis in with the idea of “equity in love relationships”. Equity theory, when applied to romantic relationships, proposes that a relationship is far more likely to be comfortable and satisfying when each individual feels they are being treated proportionally to how they are treating their partner. This sense of equity is heightened by equal social desirability, further explaining the success of ‘matched’ couples, which translates to increased stability.

So, does this mean that everyone should stop believing in the ‘fate’ and ‘magic’ of unexpected love, and simply choose their mates from pre-determined attractiveness charts? Perhaps that is the future of our species; it would certainly save a lot of time! However, as Hatfield herself told me, “Maybe we all just have to learn from bitter experiences”. For now, at least we can convince ourselves that this behaviour stems from an average human being’s subconscious. While, in real life we fall in love with a unique individual, not the expected norm.

About the Author

Prishita Maheshwari-Aplin has recently completed her school studies at Chetham’s School of Music, Manchester (UK) and hopes to achieve the required grades and take her place at Cambridge University in October to read Natural Sciences. She is passionate about science communication, especially for young people, and runs a blog with this purpose, Darwin’s Beard (darwinsbeard.net). Prishita would like to pursue a career in medical genetic research, while doing freelance science writing and blogging about exciting scientific research!